Environmental assessment report, 100 Church Street, April 2002

NYC 9/11 Public Portal Document

space above the suspended ceiling which acts as a return air plenum. Air then travels into the return air risers and returns to the 7*'’ floor fan room

The perimeter induction units, visible as units under the windows, are supplied through a supply fan located on the 7^ floor. The perimeter air handler forces air through risers running along perimeter columns. The supply risers are connected to circular ducts connected to the perimeter induction units on every floor. The return air from the perimeter units mixes with the supply air on the floors and returns via interior system return air risers. There is no dedicated return air fan for the perimeter air supply system.

In addition to the air supply from the main building HVAC system located on the 7^'’ floor, supplemental air handling units have been installed in various locations to provide additional cooling. These vary mom floor to floor generally re-circulating the building air from above the suspended ceiling through a cooling coil.

An inspection of the air handlers and ductwork indicated that visible accumulation of dust/debris was present. Although the air handlers appeared to have been partially cleaned and there was no gross debris observed which could be obviously associated with the WTC collapse, visible dust was noted. The inspection of ductwork revealed the presence of significant accumulations of dust and debris, which would not have been expected subsequent to a duct cleaning effort.

At the time of the inspection, the building had upgraded the filtering system to include high efficiency filters for particulate control. These high efficiency filters replaced the normal bag filtering system and significantly increased the filtering capability of the system that provides conditioned air to the NYCLD space.

4.2 Evaluation of Building Management Response Based on the information provided by ZAR and its environmental consultant. Ambient Group, Inc. (Ambient), the building response actions appear to have been appropriate and in conformance with NYCDEP and NYCDOH guidelines relative to clean up of WTC generated dust/debris. ZAR hired Branch Services (Branch), a New York State certified asbestos abatement company, to perform initial cleanup of gross debris at 100 Church Street. These

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